Abstract: A Raman waveguide amplifier includes a waveguide comprising a core of a Raman-active medium dimensioned and configured as a self-imaging multimode waveguide. At least one input signal is coupled into the core at a wavelength within a Raman gain spectrum of the Raman-active medium relative to at least one pump beam. The pump beam is coupled into the core so as to amplify the at least one input signal via stimulated Raman scattering to provide an output signal corresponding to an amplified replica of the at least one input signal.

Abstract: A silicon Raman laser that can be electrically switched or modulated and which demonstrates active mode-locking capabilities. The laser can be used with a more traditional glass fiber cavity, or can be fabricated on a single chip with a cavity, or a cascaded cavity, in which the chip fabrication is compatible with widely used silicon chip fabrication methods. The laser can be tuned by adjusting a source pump laser to produce specific output and operates at room temperature. Output is present in the near- and mid-infrared frequency range, and the laser can simultaneously produce output at the Stokes and at the anti-Stokes wavelengths.

Abstract: An apparatus and method for synthesizing waveforms with arbitrary amplitude, frequency, and phase modulation. Pulses from a broadband (supercontinuum) optical source are filtered into a plurality of wavelength channels, and the intensity of each wavelength channel is adjusted to an appropriate level depending on the desired shape of the envelope of the output pulse. The envelope of the sampling wavelength channels can be stretched, compressed, or inverted in the time domain later using a dispersive medium. After time domain manipulation, the optical pulse train is observed with a combination of high-speed photodetectors and a radio frequency low-pass filter, a low-speed photodetector.

Abstract: An apparatus and method for synthesizing waveforms with arbitrary amplitude, frequency, and phase modulation. Pulses from a broadband (supercontinuum) optical source are filtered into a plurality of wavelength channels, and the intensity of each wavelength channel is adjusted to an appropriate level depending on the desired shape of the envelope of the output pulse. The envelope of the sampling wavelength channels can be stretched, compressed, or inverted in the time domain later using a dispersive medium. After time domain manipulation, the optical pulse train is observed with a combination of high-speed photodetectors and a radio frequency low-pass filter, a low-speed photodetector.

Abstract: A method and apparatus for data conversion using time manipulation is disclosed. Ultrafast analog-to-digital (A/D) conversion and digital-to-analog I/A) conversion are achieved by optoelectronic time-stretching or time-compression, respectively. A pulsed laser is chirped by frequency spreading the laser output in either discrete or continuous fashion. The chirped output is then modulated with the electrical signal, and then frequency spread again. The output of the modulated signal is detected with a photodetector to convert the optical signal to a time-manipulated copy of the electrical signal.

Abstract: A heterojunction bipolar transistor in an integrated circuit has intrinsic and extrinsic base portions. The intrinsic base portion substantially comprises epitaxial silicon-germanium alloy. The extrinsic base portion substantially comprises polycrystalline material, and contains a distribution of ion-implanted impurities. An emitter overlies the intrinsic base portion, and a spacer at least partially overlies the emitter. The spacer overhangs the extrinsic base portion by at least a distance characteristic of lateral straggle of the ion-implanted impurities.

Abstract: A two dimensional encoded filter for providing wavelength and time shifted output signals is comprised of a photonic integrated device in which the input signal is optically demultiplexed into a plurality of wavelength components, fed back on optically time-delayed feedback paths to a multiplexer which reassembles the signal into a true-time delay wavelength shifted output. The photonic demultiplexer and multiplexer are comprised of a first optical star coupler having a plurality of inputs in which the center input is provided with the input signal. The first star coupler transmits the input signal across a phased array waveguide grating to a second star coupler across which the waveguide components are demultiplexed.

Abstract: A heterojunction bipolar transistor in an integrated circuit has intrinsic and extrinsic base portions. The intrinsic base portion substantially comprises epitaxial silicon-germanium alloy. The extrinsic base portion substantially comprises polycrystalline material, and contains a distribution of ion-implanted impurities. An emitter overlies the intrinsic base portion, and a spacer at least partially overlies the emitter. The spacer overhangs the extrinsic base portion by at least a distance characteristic of lateral straggle of the ion-implanted impurities.

Abstract: The inventive method of making a poly-Si emitter transistor (PET) comprises opening an emitter window in a dielectric (typically SiO.sub.2) layer, and depositing onto the thus exposed surface and/or into the single crystal Si material that underlies the exposed surface at least one atomic species. This deposition step is following by the conventional poly-Si deposition, dopant implantation and "drive-in". In a currently preferred embodiment the novel deposition step comprises a low dose, low energy As implantation (5.times.10.sup.13 -2.times.10.sup.15 atoms/cm.sup.2, 0.1-5 keV). The novel method can result in significantly improved device characteristics, e.g., in a doubling of h.sub.FE, as compared to analogous prior art PETs.